[petsc-users] 1D parallel split of dense matrix

[Yann Jobic]

Hi all,

I want to decompose a matrix in parallel for only one direction, the 
columns, for a dense matrix, loaded from a binary file. I tried to use :
MatCreateDense(PETSC_COMM_WORLD,NumberOfRhs,matLocNbCols,NumberOfRhs,matNbCols,NULL,&NRhs);
with matLocNbCols the number of local columns of a linear system (matrix A).
However i've got an error when i use MatLoad : Read from file failed, 
read past end of file.
Maybe because the number of local rows is equal to the number of global 
ones (variable NumberOfRhs) ?
The sequential version runs fine.

Is it possible ?

I'm trying to set up a specific rhs matrix in order to solve the same 
linear system (ksp) with different right hand sides (rhs).
In order to do so, i transposed the matrix containing all the rhs in a 
file, which i would like to load in parallel. The idea is to use 
MatGetRow, in order to create the rhs Vec, and then call KSPSolve (the 
inverse matrix of A should have been kept).

However, i would like a particular setup (1D parallel split) for the 
parallel layout of the rhs matrix : The number of columns of A is equal 
to the number of column of the matrix rhs, and the number of rows of rhs 
is equal to the number of rhs that i want to solve. I want this rhs to 
be split in the same way of the linear system, and i want each 
processors to have the whole global number of rows, that is to say, i 
want a 1D decomposition of my rhs matrix (corresponding to MatCreateVecs).

I then have to copy a row of rhs in a vec, and solve, for all the rows 
of rhs.

Is it a bad way to handle a N rhs problem with KSPSolve ?

Thanks,

Yann

ps : the error :
Reading ComplexMatrix.bin Matrix...
Matrix ComplexMatrix.bin read
global size of A matrix (583335,583335)
PROC : 1 Number of local  columns of the matrix A   : 291667
PROC : 1 Number of local  columns of the vector     : 291667
global size of NRhs Matrix : (15,583335)
PROC : 0 Number of local  columns of the matrix A   : 291668
PROC : 0 Number of local  columns of the vector     : 291668
Reading NRhs ComplexRhs.bin Matrix...
[0]PETSC ERROR: --------------------- Error Message 
--------------------------------------------------------------
[0]PETSC ERROR: Read from file failed
[0]PETSC ERROR: Read past end of file